Electrolytic method of etching metals with stencils



March 8, 1949.

P. l. NAGLE ELECTROLYTIC METHOD OF ETCHINQ METALS WITH STENCILS v Filed April 8, 1945 MW m INVENTOR, 1 BY Per/y] a gk,

Patented Mar. 8, 1949 2,463,711 ELECTROLYTIC METHOD OF ETCHING METALS WITH STENCILS Perry I. Nagle, Chicago Heights, Ill. Application April 8, 19 13, Serial No. 482,234

(Cl. 204-l43) 3 Claims.

The present invention relates to novel means for and method of etching characters or indicia, designs and the like upon the surface of metals and. other similar material.

One of the objects of the present invention is to provide a novel process for etching the surface of metals in any desired form, which can be practiced with ease, with accuracy and at small cost.

Various methods of etching the surface of metals are known at the present time, one of which, for example, involves the application of a protective coating to the surface of the metal, after which the desired design or characters are scratched into the said protective coating with a stylus or the like, and then an acid used to cut into the metal at the points where the protective coating has been removed to form the said design.

A further illustration of this art involves the use of some varnish or the like, such as gum guaiacum, which is painted upon the surface of the metal, after which the same is stamped with some alkaline material such as caustic soda to form the design characteristics of the stamp upon the surface of the metal. In addition, etching of the metal surface may be accomplished by certain well-known photographic methods.

Procedural difficulties characterize certain of these well-known methods in the art, the principal one being that the formation of the characters or designs must take place in situ upon the metal, which requires tedious and expensive manual work upon the surface of the material to be etched. Furthermore, where the work is dependent upon manual skill of the operator, the design or characters of successive pieces or articles lack that uniformity which characterizes the designs and indicia formed by a machine operation. The desirability of forming a stencil or masking sheet separately and then applying the same to the work to be etched has been recognized for some time, but has not been found satisfactory because of the operators inability to produce sharp and distinct characters or designs upon the work.

The present invention accordingly has as its principal object the provision of a novel process involving the steps of forming a stencil or masking sheet separately, applying the sheet to the work on which the etching is to be performed, and causing the said metal to be etched electrolytically.

The present invention is predicated upon the the development of use of a suitably treated stencil-sheet which is conditioned to provide well defined indicia, characters or any other designs, and to assure close adherence of the said stencil or masking sheet to the work, whereby such sharp and well defined characters are etched upon the metal surface by an electrolytic process which follows. The present invention contemplates the use of stencilsheets formed in accordance with the Hill Patent No. 1,526,982, or their equivalents. The stencilsheets of that patent comprise a base of Y0- shino paper to which is applied a pressure impressionable coating comprising a cellulose compound or cellulose ester, such as cellulose nitrate or cellulose acetate, and which may contain either or both a tempering agent and a setting agent, the former being an oil, and the latter consisting of a fatty or tallow-like ingredient.

The present invention accordingly has as a further object the idea of stencilizing a stencilsheet formed in accordance with the said Hill patent. conditioning the stencil, applying the same to the metal or other surface to be etched, and electrolytically etching the metal surface or the like to conform to the said stencilized portion of the stencil.

More particularly the present invention involves the step of conditioning a stencil of the type hereinabove indicated, which conditioning comprises the application of a solvent and wetting agent to the coating thereof, the agent serving in the capacity of rendering the coating pliable and soft to such an extent as to cause the stencil to have intimate contact with and to adhere to the work, which conditioning assures the formation of clear, well defined characters and the like during the subsequent etching step. Such an agent further functions to remove any residual cellulose compound entrapped within the stenilized portion of the stencil so as to assure well defined characters, indicia or design in the final etching step.

The present invention further contemplates an etching procedure involving the conditioning of a stencil such as above described, and to incor porate an electrolyte within the stencilized portion thereof whereby the etching procedure may be facilitated and expedited.

Another object of the present invention is to provide a novel etching process which can be performed without the formation of excessive amounts of gas under the stencil, which would otherwise cause uneven and ragged edged designs or characters, and without loading upv the stencil with insoluble or otherwise objectionable salts which would prevent the carrying out of the etching procedure to secure the results desired.

A further object of the present invention is to provide a novel conditioning material for a stencil which may be used in following the process herein disclosed.

Still another object of the present invention is to provide a novel electrode for use in electrolytic'ally etching metals involving the provision of a body of absorbent material and a metal supporting element therefor between which is a layer of lead having the property of preventing the formation of insoluble and nonconductive salts on the electrode which would otherwise clog the electrode and prevent successful etching in accordance with the processes herein disclosed.

Other objects, features, capabilities and advantages are comprehended by the invention, as will later appear and as are inherently possessed thereby.

Referring to the drawings- Figure l is a view in perspective of the equipment used in etching the surface of metal, the same disclosing the stencil as applied to the work being etched; and

Figure 2 is a view in section taken through the electrode of the device shown in Figure 1 of the drawing.

As hereinbefore mentioned, the present invention is primarily concerned with an etching procedure in which the stencil-sheet or mask can be separately stencilized before application to the surface of a metal object or the like to be etched.

'Ihis is of particular significance and a distinct advantage in this field inasmuch as the stencil sheets may be separately stencilized by placing the same in a typewriter or under any other pressure applying machine, during which the same may have impressed into the surface thereof any selected design, indicia, character or the like, to assure uniformity in etching on successive pieces or articles to which the stencil may be applied. The stencilized sheets or masks are then conditioned and applied to the work, after which the same are subjected to an electrolytic etching procedure to etch the surface of the metal or the like in accordance with the design appearing upon the stencil.

In following the present process, stencil-sheets made in accordance with the disclosure of the Hill patent hereinabove referred to, may be placed in a typewriter and characters or other indicia impressed onto the surface thereof in accordance with the desires of the operator. On the other hand, these stencil-sheets may be subject ed to any other pressure applying means, such as a printing press or the like, to be impressed with any design or characters selected by the operator.

After these sheets are stencilized in the manner above described,

pound. The conditioning of these stencils in accordance with the present invention involves the use of one or more materials which soften the film or coating to render the same tacky, so that it will stick or adhere to the work to form Well defined characters or designs on the surface thereof. The material used in this conditioning step likewise serves to remove any residual cellulose compound entrapped Within the stencilized portions of the stencil to secure sharp and well defined characters, indicia, etc. In addition, the material used is particularly adapted for conditioning the stencilized portions of the sheet whereby the same are readily wettable with the electrolyte to assure proper etching of the metal or the like.

The conditioning material used is further characterized as being particularly adapted for assuring the passage of electrical current through the stencilized portion of the stencil only and not through the unstencilized portion thereof.

The present invention is predicated upon the discovery that the stencils of the type contemplated herein can be efi'ectively conditioned by ethyl lactate so that a highly desirable etching of the metal or the like can be efiected. It has been found that ethyl lactate will soften the coating of such stencils to the proper consistency so that the stencil can be readily handled, and will cause the stencil to adhere to the metal or the like to produce well defined and exceedingly satisfactory etching. Since ethyl lactate is not volatile, the stencils will remain in such intimate contacting relation to the metal a sufficient length of time for the etching procedure. Ethyl lactate also possesses other of the properties desired, as tabulated above, and in addition is an excellent wetting agent for the electrolyte used for etching.

While not essential to the practice of the present invention, other ingredients may be added to the ethyl lactate to produce certain additional and desirable results. For example, in order to expedite the etching of the surface of the metal body or the like, the conditioner may further include an electrolyte. Any electrolyte may be used which does not form excessive amounts of gas under the stencil and which does not form insoluble or otherwise objectionable salts in the stencil itself and in the pad of the electrode (to be more fully described hereinafter). As an example, sodium chloride, ammonium chloride or ammonium bromide may be used. However, ammonium bromide is preferred to any of the electrolytes which may be used. It is to be understood, however, that the introduction of the electrolyte to the conditioner is not essential to the process herein involved either when the same comprises ethyl lactate alone or combined with other ingredients hereinafter to be disclosed.

Furthermore, the conditioner may include an agent having the property of increasing the bonded relation of the stencil to the work and to make the same adhere closely thereto. A material suitable for this purpose is ethylene glycol, which has the property of being a wetting agent as well as a softening and swelling agent, and is not volatile. It also has the property of being a tempering or diluting agent serving to control solubility of the cellulose ester film on the stencil by ethyl lactate and other solvents.

The conditioning solution also may include a solvent in which the cellulose compound of the stencil is highly soluble. Diacetone alcohol and acetone have been found suitable for this purpose, either one or both of Which may be used in the conditioner. Small amounts of either one or both of these solvents is all that is necessary and the capacity of removing the any residual cellulose compounds remaining in the fibers of the stencil to assure Well defined :haracters and designs, and sharp margins, and 50 facilitate the electrolytic etching procedure. it is essential, however, that these solvents be used in small proportions, otherwise the cellulose film or coating of the stencil will become smeared and produce an unsuitable etching of the work. A conditioner particularly adapted for treating stencils according to the present invention may comprise the following constituents in the proportions indicated:

Cubic centimeters Ethyl lactate 50 Ethylene glycol A 10 Diacetone alcohol 5 Acetone 5 Ammonium bromide 5 The stencils may be conditioned by the application of small quantities of this conditioner to the coating thereof in any conventional manner. After the stencil is so conditioned the same may be applied to the work and the work etched, as will presently be described.

To facilitate the full disclosure of the present invention, reference may be made to Figure 1 wherein a conditioned stencil, identified by the reference numeral 2, is shown in position upon the work 4. After application of the stencil to the work, the same is rolled or pressed to secure proper adhesion and contact of the same to the work. This work 4 is included as an anode in a direct current circuit 6, having a source of electrical energy 8, and which further includes the electrode l constituting the cathode of the electrical circuit. The electrode handle l2 and a retaining or supporting element 14 at its forward end connected to the metal wire l0 within the circuit 6, which retainer is, in the present illustration, formed of spring brass. The retainer or support is adapted to absorbent material 16, which may be of felt or the like, and which holds the electrolyte for the etching process. The etching process consists of applying the electrolyte to the absorbent material !6, after which the same is moved over the stencilized surface, such as l8, formed in the body of the stencil 2. a

The electrolyte may consist of the following ingredients, the same being illustrative of'a suitable electrolyte for the etching procedure according to the present disclosure:

Water cc 50 Ammonium bromide "grams" 5 Ethylene glycol cc 5 Trace of iodine It is, of course, appreciated that the ammonium bromide is the active ingredient in this electro lytic solution and accomplishes the etching of the metal. The ethylene glycol prevents freezing of the electrolyte and facilitates miscibility with the wetted portion of the stencil. The iodine is primarily included as a coloring agent.

As hereinbefore pointed out, in a process of the type herein disclosed, it is essential to provent the formation of excessive amounts of gas between the stencil and the metal being etched, and to avoid loading up either the stencil or the electrode with insoluble and non-conductive as well as other objectionable salts. The use of ammonium bromide as a principal ingredient of the electrolyte assures that these excessive gases are not formed between the stencil and the work. In order to prevent the formation of insoluble and non-conductive salts in the electrode of the device herein disclosed, it was found that the i0 is formed with a hold a body of absorbent pad should be protected from the metal retainer l4. Accordingly, the said absorbent pad is separated from the metal retainer H by a layer of lead, which may be in the form of a rather thick foil completely separatin the absorbent pad from the metal retainer 14. By the use of this layer of lead, load-up of the stencil and electrode is avoided and continued use of the same for long periods of time secured.

Inasmuch as ethyl lactate is an excellent wetting agent in this process, and the other materials, such as ethylene glycol, diacetone alcohol and acetone, are likewise wetting agents, it is only necessary to place small quantities of the conditioner upon the absorbent material H5 at any one time. Upon application of the felt sponge or absorbent material Hi to the stencilized portion of the stencil 2, the electrolyte, acting as a conductor of electricity through the stencilized portion of the stencil, causes the etching of the work.

The present invention is primarily characterized by the discovery that ethyl lactate will condition a stencil of the type herein disclosed, whereby metal work and the like can be satisfactorily etched in accordance with the process herein disclosed. Furthermore, this material has the property of making the film tacky without drying out, and the stencil will accordingly adhere to the work for some period of time sufficient to etch the metal surface of the work. It renders the fibers of the stencilized portion of the stencil capable of being wetted with electrolytes but does not make the unstencilized portion of the stencil a conductor of electricity, so that by its use one can be assured that the only etching occurs at the stencilized portion and that the same is well defined, with sharp margins forming the characters, indicia or any other design, thus making a highly desirable etching which can be used for marking tools with names to identify ownership, sizes or other descriptive purposes. It is also understood, of course, that any suitable design may be incorporated in the stencil.

As hereinabove used, and as appears in the claims, stencilizing is to be understood to mean the application of pressure to the surface of a stencil sheet to form characters, indicia, designs, etc., which are to be transferred to or duplicated on the surface of various metal objects by an etching step.

While I have herein described illustrative embodiments of the invention and processes for making the same, it is to be understood that the invention is not limited thereto but may comprehend other details, features and process steps without departing from the spirit of the invention.

I claim:

1. A process of etching metals, comprising the steps of stencilizing a stencil sheet which is formed with a base having a pressure impressionable plastic coating including a cellulose ester selected from the group consisting of cellulose acetate and cellulose nitrate, then conditioning said stencil by the application of ethyl lactate to said coating to soften the coating on the stencil whereby to facilitate the adherence of the stencil to metal, placing said conditioned stencil and metal to be etched in surface contact with one another, and electrolytically etching said stencil coated metal to conform to the stencilized portion of said stencil.

2. A process of etching metals, comprising the steps of stencilizing a stencil sheet which is formed with a base having a pressure impressionable plastic coating including a cellulose ester selected. from the group consisting of cellulose acetate and cellulose nitrate, then conditioning said stencil by the application of a conditioning solution to the same, said conditioning solution containing ethyl lactate and ethylene glycol, placing said conditioned stencil and the metal to be etched in surface contact with one another, and electrolytically etching said stencil coated metal to conform to the stencilized portion of said. stencil.

3. A process of etching metals, comprising the steps of stencilizing a stencil sheet which is formed with a base having a pressure impressionable plastic coating including a cellulose ester selected from the group consisting of cellulose acetate and cellulose nitrate, then conditioning said stencil by the application of a conditioning solution to the same, said solution containing ethyl lactate, ethylene glycol, and an etching electrolyte, placing said conditioned stencil and the metal to be etched in surface contact With one another, and electrolytically etching said stencil coated metal to conform to the stencilized portion of said stencil.

PERRY I. NAGLE.

8 REFERENCES CITED The following references are of record in thl file of this patent:

UNITED STATES PATENTS Number Name Date 276,893 Schulze-Berge May 1, 1883 1,094,837 Dick Apr. 28, 1914 10 1,169,520 Strippel Jan. 25, 1916 1,552,796 Donohue Sept. 8, 1925 I 1,639,080 Davis Aug. 16, 1927 1,891,962 Tseng Dec. 27, 1932 2,172,158 Brislee et a1 Sept. 5, 1939 2,234,064 Ulano et al Mar. 4, 1941 2,244,620 Hesse June 3, 1941 2,283,171 Batcheller May 19, 1942 2,333,624 Altman et a1 Nov. 9, 1943 FOREIGN PATENTS Number Country Date 551,771 Great Britain Mar. 3, 1943 OTHER REFERENCES Industrial Solvents, by Mellan (1939), page 379; Reinhold Publishing Corp. 

